This application claims priority to prior foreign application No. UK 0022157.2, filed Sep. 9, 2000.
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The present invention relates to apparatus and methods for use in wireline valves or, particularly but not exclusively used in the oil and gas industries.
Conventionally, ram assemblies are used inside a wireline intervention product called a wireline valve, and the sole purpose of ram assemblies is to provide a safety barrier against well pressure whilst remedial work is carried out on the wire. Such remedial work may be required if for example, the wire has a broken strand or has xe2x80x9cbird cagedxe2x80x9d which causes the wire to get jammed in another piece of equipment, such as a greasehead which is located at the top of the intervention string above the wireline valve. In such a scenario, the only known solutions to this problem are either to chop the wire and fish it out afterwards or to seal around the wire below the problem area. A wireline valve is used to perform the latter solution.
The high pressures inside the well mean that, conventionally, the only reliable way to achieve a seal in the wireline valve is with rubber seals mounted on the inner most faces of the ram assemblies. A middle portion of the outer surface of the rubber seals comprise a recess which conforms to the outer surface of the wireline, and grease is pumped into the inner armours of the wireline; the viscosity of the grease drops the pressure within the inner armours. However, at these high pressures, rubber tends to behave like a fluid and as such needs something to prevent it being flushed away by the pressure. The common solution to this problem is the use of steel plates which retain the rubber in place. Therefore, the wireline has to be brought into a specific area of the ram seal so that when the ram assemblies are closed, the remaining rubber that is not involved in sealing around the wire is also backed up by steel. Currently this is achieved by guiding the wire into the middle of the well bore where the recess in the ram seal is located.
There are three main different types of mechanism for guiding the wire into the middle of the well bore, these being:
1) Flat plate replaceable guide rams, as shown in FIG. 1. These were the first type of guides to be offered in the market place and are probably the most straightforward to manufacture. However they suffer the disadvantage that the guides cannot, under certain geometry""s, be made to pick up a wire located at the edge of the through bore, and there is also a possibility that the guides could be dropped down the well;
2) Curved replaceable guide rams, as shown in FIG. 2. These rams have curved guides allowing them to pick up the wireline from the very edge of the throughbore of the wireline valve. However, they also suffer from the disadvantage that the guides could be dropped down the well; and
3) Integral guide rams, as shown in FIG. 3. These rams have the guides formed integrally with the ram assemblies, and were produced to solve the problems of bits dropping down the well as discussed in 1) and 2) above. These rams also provide greater mechanical strength to the ram assembly when closed, as the guide fingers interlock in the opposing ram bore creating a span beam in bending rather than a cantilevered beam. This has allowed the use of these integral guide rams in higher pressure wireline valves such as 15000 p.s.i. sets. However, these rams suffer from the disadvantage that they are expensive to manufacture, due to the more complex machining required.
Recently, there has been a significant increase in the number of incidents where the ram assemblies of various wireline valves have been closed and, instead of guiding the wire and sealing around the wire, the ram assemblies have crushed or completely cut the wireline. This is obviously not acceptable.
Extensive testing has shown that under certain conditions of wire tension and angle through the wireline valve, all of the above ram types 1), 2) and 3) may crush or cut the wireline and it has also been determined that none of them will guide a slack wire into the correct position.
In accordance with a first aspect of the present invention, there is provided an apparatus for moving an elongate member which passes through a throughbore of a valve device, the apparatus comprising an upper movement mechanism and a lower movement mechanism spaced apart about a portion of the valve device, the upper and lower movement mechanisms being actuable such that the elongate member is moved into a pre-determined position.
In accordance with a second aspect of the present invention, there is provided a method of moving an elongate member which passes through a throughbore of a valve device, the method comprising providing an upper movement mechanism and a lower movement mechanism spaced apart about a portion of the valve device, the upper and lower movement mechanisms being actuable such that the elongate member is moved into a pre-determined position, and actuating the upper and lower movement mechanisms.
The elongate member is typically a wireline, logging line, cable or the like. The predetermined position is typically a position substantially parallel to a longitudinal axis of the valve device and more preferably is substantially co-incident with the longitudinal axis of the valve device, such that the upper and lower movement mechanism are preferably respective upper and lower centralising mechanisms.
In a preferred embodiment, the upper centralising mechanism comprises at least one pair of guide arms which are adapted to move the elongate member toward the longitudinal axis, typically upon movement of the guide arms in a direction substantially perpendicular to the longitudinal axis of the valve device.
More preferably, the upper centralising mechanism comprises two pairs of said guide arms. Typically, one pair of guide arms of the upper centralising mechanism are provided on a first ram assembly, and a second pair of guide arms of the upper centralising mechanism are provided on a second ram assembly. Typically, the first and second ram assemblies are arranged substantially diametrically opposite one another about the longitudinal axis of the throughbore. Preferably, each of the pair of guide arms of the upper centralising mechanism are arranged about a recess adapted to accept the elongate member therein, and more preferably, each of the pair of guide arms taper outwardly at an angle from the longitudinal axis of the respective ram assembly, where said angle may be in the region of 60xc2x0 to 45xc2x0. Preferably, each pair of guide arms of the upper centralising mechanism taper outwardly to an extent at least as great, and preferably greater than, the diameter of the throughbore of the valve device.
More preferably, the lower centralising mechanism comprises two pairs of said guide arms. Typically, one pair of guide arms of the lower centralising mechanism are provided on a first ram assembly, and a second pair of guide arms of the lower centralising mechanism are provided on a second ram assembly. Typically, the first and second ram assemblies are arranged substantially diametrically opposite one another about the longitudinal axis of the throughbore. Preferably, each of the pair of guide arms of the lower centralising mechanism are arranged about a recess adapted to accept the elongate member therein, and more preferably, each of the pair of guide arms taper outwardly at an angle from the longitudinal axis of the respective ram assembly, where said angle may be in the region of 60xc2x0 to 45xc2x0. Preferably, each pair of guide arms of the lower centralising mechanism taper outwardly to an extent at least as great, and preferably greater than, the diameter of the throughbore of the valve device.
The pair of guide arms of the upper centralising mechanism of one of the ram assemblies is preferably arranged to butt against a portion of the pair of guide arms of the upper centralising mechanism of the other of the ram assemblies, and more preferably, is arranged to butt against in a close fitting manner. Typically, a surface of the pair of guide arms of the upper centralising mechanism of one of the ram assemblies is preferably arranged to be a sliding fit with a surface of the pair of guide arms of the upper centralising mechanism of the other of the ram assemblies. The sliding fit arrangement provides the advantage that, as the guide arms are brought together, the elongate member is denied the opportunity to be trapped between the two sliding surfaces.
The pair of guide arms of the lower centralising mechanism of one of the ram assemblies is preferably arranged to butt against a portion of the pair of guide arms of the lower centralising mechanism of the other of the ram assemblies, and more preferably, is arranged to butt against in a close fitting manner. Typically, a surface of the pair of guide arms of the lower centralising mechanism of one of the ram assemblies is preferably arranged to be a sliding fit with a surface of the pair of guide arms of the lower centralising mechanism of the other of the ram assemblies.
Typically, the recesses of the upper centralising mechanism and the recesses of the lower centralising mechanism are arranged to be coincident with the longitudinal axis of a recess of an inner sealing member of the valve device.
Most preferably, each of the pair of ram assemblies comprises an upper and lower centralising mechanism. Typically, the upper and lower centralising mechanism are located immediately about an inner sealing member of the wireline valve.
In an alternative embodiment, the upper, and preferably the lower, centralising mechanism comprises a pair of rotatable guide arms which are adapted to move the elongate member toward the longitudinal axis. Typically, each rotatable guide arm comprises a substantially semi-cylindrical guide arm which may be rotated about its diameter, such that rotation of the pair of guide arms toward one another causes the elongate member to move toward the longitudinal axis of the throughbore of the valve device. Typically, the upper centralising mechanism is formed within a tubular member which can be coupled to the upper end of the valve device. Typically, the lower centralising mechanism is formed within a tubular member which can be coupled to the lower end of the valve device.
In a further alternative embodiment, the upper, and preferably the lower, centralising mechanism comprises a pair of moveable members coupled to one another by a linkage mechanism such that rotation of one of the moveable members relative to the other causes the other moveable member to move toward the rotating moveable member, and also causes the linkage mechanism to move toward one another at their centre point, and are adapted to move the elongate member toward the longitudinal axis of the through bore of the valve device. Typically, the upper centralising mechanism is formed within a member having a substantially cylindrical throughbore, wherein the member can be coupled to the upper end of the valve device. Typically, the lower centralising mechanism is formed within a member having a substantially cylindrical throughbore, wherein the member can be coupled to the lower end of the valve device.
In a yet further alternative embodiment, the upper centralising mechanism is provided within a member having a substantially cylindrical throughbore, wherein the member can be coupled to the upper end of the valve device. Typically, the lower centralising mechanism is formed within a member having a substantially cylindrical throughbore, wherein the member can be coupled to the lower end of the valve device. Typically, the upper and lower centralising mechanism each comprise a plurality of moveable fingers coupled in the form of an iris of a camera, such that upon actuation, the fingers reduce the cylindrical throughbore of the member to a size slightly larger than the diameter of the elongate member.